A fuel cell is a device which is operable to receive a fuel reactant susceptible to being oxidized and an oxidizing agent reactant, and to oxidize the fuel reactant using the oxidizing reactant to directly generate useable electrical power; the fuel reactant is, for example, a hydrocarbon and/or hydrogen. Moreover, the fuel cell is attractive in that it is devoid of complex moving parts, for example in contradistinction to contemporary combustion engines which include rotating and/or reciprocating components susceptible to wear and noise generation. Furthermore, the fuel cell is potentially capable of being constructed so as provide sufficient electrical power for operating transport systems, emergency power supplies and similar.
In overview, several fuel cells are contemporarily connected together in various configurations to provide fuel cell packs which are operable to provide elevated electrical output potentials, for example 10's of volts. A schematic example of a fuel cell is indicated generally by 10 in FIG. 1. The fuel cell 10 includes an electrolyte 20. The electrolyte 20 is provided with at least one anode electrode 30 and at least one cathode electrode 40, such that the at least one anode electrode 30 is isolated spatially and electrically from the at least one cathode electrode 40. Optionally, the electrolyte 20 is implemented as a substantially planar panel having first and second principal surfaces 50, 60; however, alternative implementations of the electrolyte 20 are feasible. One or more cooling cells 70 are optionally included in the fuel cell 10 in relatively close proximity to the electrolyte 20 and are operable to maintain the fuel cell 10 at an optimal temperature in use the one or more cooling cells 70 are beneficially provided with fluid coolant flow therethrough for removing heat energy therefrom; such fluid can be a liquid or a gas. However, in the context of fuel cell technology, a term “fluid” is often used to specify a liquid.
When the fuel cell 10 is in operation, a first reactant 80 is directed to flow over an active region of the at least one anode electrode 30; moreover, a second reactant 90 is directed to flow over an active region of the at least one cathode electrode 40. An oxidizing reaction arising between the first and second reactants 80, 90 in a vicinity of the electrolyte 20, whereat the first reactant 80 is oxidized and the second reactant 90 is reduced, is operable to generate both positive and negative charges. The positive and negative charges have mutually different rates of propagation through the electrolyte 20, thereby causing a potential difference V to be generated between the at least one anode electrode 30 and at least one cathode electrode 40. Ideally, only protons are transported through the electrolyte 20 when the fuel cell 10 is implemented as a PEM-type fuel cell; “PEM” is an abbreviation for Proton Exchange Membrane. In such a PEM-type fuel cell, electrons complementary to the protons are then available for flowing in an external circuit.
The potential difference V enables an external current I to be extracted by a load L connected in operation between the at least one anode electrode 30 and at least one cathode electrode 40. The electrolyte 20 is susceptible to becoming less effective during use, for example due to increased charge resistance and/or resistance to ion transport therethrough, and areas of the electrodes 30, 40 are susceptible to become progressively less active. Moreover, the fuel cell 10 is susceptible to being operated at elevated temperatures, for example in a range of 80.degree. C. to 200.degree. C., which accelerates degradation of the fuel cell 10 due to ageing of its seals and corrosion of its component parts. Such degradation of fuel cell performance during operation dictates fuel cell replacement or repair after a given period of use which requires that fuel cell manufacturing costs are sufficiently competitive in comparison to alternative approaches to generate mechanical and/or electrical power from oxidation processes. Alternative approaches include, for example, internal combustion engines: optionally, the internal combustion engines are mechanically coupled to electrical generators for generating electricity.
Thus, fuel cells have a finite operating lifetime before their effectiveness to generate electrical power is directly diminished. In view of such finite operating lifetime, it is desirable to manufacture such fuel cells as efficiently and economically as possible so that they are capable of providing a commercially competitive solution to other devices capable of generating useable power from fuel oxidation, for example hydrocarbon and/or hydrogen oxidation.
It is known from a published PCT patent application no. WO2004/027910 to manufacture a fuel cell by stacking component parts together. The components are designed so that, when assembled together, they cooperate to provide channels. Flows of reactants are directed in operation through the channels to pass active surfaces of electrodes. Moreover, optionally, flows of cooling fluid are directed through other of the channels to codling cells which are operable to remove heat energy from the fuel cell. The components are implemented as planar parts which are potentially delicate to handle during manufacture and which need to be mutually aligned and overlaid when fabricating the aforesaid fuel cell. Such handling of components is an at least partially serial assembly process which is time consuming and hence represents a costly manner of manufacture. Moreover, when progressively more such components are assembled together into a stacked configuration, there is progressively more effective investment vested in the stacked configuration. Furthermore, a risk that one or more of the components are incorrectly mutually positioned or that at least one of the components is defective increases as the stacked configuration includes more components. Disassembly of the stacked configuration to replace a defective component therein is often commercially unattractive and can therefore risk generating expensive waste.
In a United States patent application no. US 2003/0221311, there is described a method of assembling components of a membrane electrode sealed assembly. The method includes:
(a) a first step of unrolling a first cell section from a gasket roll;
(b) a second step of aligning a first cell section of a first gas diffusion layer with the first cell section of the first gasket roll;
(c) a third step of aligning a first cell section of a membrane layer with the first cell section of the first gas diffusion layer;
(d) a fourth step of aligning a first cell section of a second gas diffusion layer with the first cell section of the membrane layer;
(e) a fifth step of locating a first catalyst layer on one of the membrane layer and the first gas diffusion layer prior to the first cell section of the membrane layer being aligned with the first cell section of the first gas diffusion layer;
(f) a sixth step of locating a second catalyst layer on one of the second gas diffusion layer and the membrane layer prior to the first cell section of the second gas diffusion layer being aligned with the first cell section from the second gasket roll; and
(g) a seventh step of aligning the first cell section from the second gasket roll with the first cell section of the second gas diffusion layer. The aforementioned US patent application also discloses variants of the method but all involve considerable working of the membrane during fabrication of a membrane electrode sealed assembly.
The method described in the aforesaid published United States patent has associated therewith certain technical problems. A first problem is that the membrane web is introduced in step (d) and is thereby susceptible to being stressed when other parts are later bonded thereto. Moreover, the method is not a completely continuous process for fuel cell manufacture as certain molding operations are involved which potentially limit manufacturing throughput. Furthermore, the method is essentially without feedback to cope with potential defects arising during fabrication of the membrane layer with its associated catalysts.